A quantitative accounting of drug transport, distribution and loss in the eye, from an applied dose, has not been fully reported for any ophthalmic drug. In addition, the levels of drug in eye tissues as a function of number of doses, time between doses and dose size has also not been investigated. This situation is somewhat surprising since this information is essential for the development of mechanisms of drug transport and elimination as well as the more clinically applied aspects of proper dosing regimens, construction and evaluation of new drug delivery systems and further insight into ocular drug toxicity problems. The present work determined the disposition of pilocarpine nitrate in cornea, lens, iris, ciliary body and vitreous humor following a single topical dose of drug. The data was fitted to a four compartment kinetic scheme that adequately described the drug disposition and provided the associated rate and equilibrium constants for the various compartments (tissues). From the four compartment model a multiple dose study was initiated in which drug levels in the various tissues after multiple dosing were predicted. There was excellent agreement between predicted and found drug levels in the various tissues. Additional work will include variation in the dosing pattern as well as conducting the study in pigmented animals. Data from this study will provide a sound basis for dosing regimens as well as insight into ocular drug toxicity problems that result from drug accumulation.